Theranostic nanocarriers combining high drug loading and magnetic particle imaging.

We report preparation of theranostic nanocarriers loaded with up to 50 wt% of the anticancer drug doxorubicin that contain magnetic nanoparticles which enable Magnetic Particle Imaging (MPI), an emerging technology for quantitative and unambiguous imaging of the nanocarriers. The nanocarriers, coated with poly(ethylene glycol)-block-poly(lactic acid) (PEG4.9kD-b-PLA6kD) block copolymer for colloidal stability, are composed of a hydrophobic core of precipitated hydrolysable doxorubicin prodrug (proDox) and magnetic nanoparticles. Transmission electron microscopy (TEM) shows evidence of precipitated proDox for nanocarriers with high drug loading of up to 50 wt%. MPI measurements show that the nanocarriers can be quantitatively imaged. The nanocarriers are internalized by MDA-MB-231 cells and their IC50 value via metabolic assay is 1.1 µM, compared to 0.21 µM for free doxorubicin. The release rate from the nanocarriers was dependent on environmental pH. These nanocarriers with high drug loading and quantitative imaging are promising candidates for future applications.